Boundary conditions using FEM 1

[SuperViriato]

Im tryng to use FEM to make a model of a cell of a typical laminate composite. In this fase im comparing known results of material properties (like young modulus and so on) with the data given to me by a FEM program (ADINA) and FE models i create for each test.

Im having trouble defining the boundary conditions for some of the models.

Its easy to explain my problem using pictures...so i put them on the net:

http://www.geocities.com/drviriato/index.htm

I must excuse myself because of my bad inglish! i hope someone can help me!

 

[crisb]

Try fixing the symmetrical surfaces in the direction normal to the surface ONLY. Then fix the MINIMUM number of points in the other axes to stop any rigid body movement.

 

[corus]

To keep the top surface plane you have to link all the freedoms on the face to any node on that face in the direction normal to that face. Symmetry applies to the faces normal to the quarter circle planes. I'd also think about putting a few more elements through the thickness too.

corus

 

[gwolf]

Yes I agree, more elements through the thickness.

You have correctly applied the symmetry boundary condition for the single fibre but you have forgotten the other implied symmetry planes with the adjacent fibers.

Hope this helps,

Gwolf.

 

[crisb]

In ADINA you can use Model>Constraints>Constraint_equations, to keep for example the top surface in plane. Try setting the slave as the surface, master as a point on that surface and then constrain DOF's in the axis normal to the surface.

 

[SuperViriato]

Thanks for the help people.
I was able to resolve my problem. It was about the right
boundary conditions.

A very special thanks to 'Crisb' for his help.

It was my first time at 'Eng-tips forum' and im very
pleased, im considering donating some $, i think this
forum deserv it!

 

[johnhors]

SuperViriato

You say "A very special thanks to 'Crisb' for his help" then you should at least award him a star for his help to you !

 

[SuperViriato]

Im sorry, im new here 'Johnhors'. But i already corrected my mistake. A full star for 'Crisb', is tip was very helpfull. But i must thank again everyone that posted and tryed to help...i hope one day i can help all of you in return!